An experimental surface ionization tandem mass spectrometer has been constructed and is being tested for the analyses of polar organic compounds in complex mixtures of biological origin. Phospholipids, drug metabolites and small peptides are being partially purified and analyzed by liquid surface ionization techniques. A microwave interface to convert organic compounds eluting from a capillary gas chromatograph to simple di- or triatomic species has been refined and tested on two mass spectrometers with oxygen and hydrogen as reagent gases. Specific nuclides such as 13C, 14C, N, S, halogen, etc. can be detected with high sensitivity. The goal of both mass spectrometric developments is to devise new tools to solve intractable or presently difficult analytical problems in pharmacology and neuroscience.